In the oil and gas industry, numerous types of tubular members are employed as, for example, in the drilling, completing and producing aspects of oil and gas wells. Among the tubular members employed are tubing and casing. In the manufacture of these oilfield tubulars, e.g., tubing or casing, it is typical to start with a piece of unthreaded or green pipe and cut male or pin threads on both ends of the pipe (pin-x-pin). In use, the pin-x-pin pipe sections are connected to one another by a coupling, typically a relatively short tubular member having a female thread or box connection at each end, to form a tubing or casing string.
In a typical threading line for tubing, casing or the like, a load of pipe is deposited on a rack or table. The pipe, referred to as green pipe, is then indexed onto a conveyor which can both rotate and translate the pipe into a first threading station comprising a lathe until it contacts a pipe stop at which time the chucks on the lathe clamp the pipe and the threading cycle begins to cut the desired threads on that end of the green pipe. Following threading of one end of the first end of the green pipe, the pipe moves to an inspection station which typically can comprise popup rollers which slowly rotate the pipe while it is gauged and de-burred, if necessary. Upon completion of inspection, the pipe moves onto a second threading station when the identical chain of events occurs vis-à-vis threading and inspecting. After inspection, the fully threaded pipe moves to a blowout station where coolant and chips are blown out of the pipe by compressed air. Upon completion of blowout, the fully threaded pipe rolls down to a bucking unit table and is fed into a bucking unit where a coupling is generally bucked onto the pipe. After the coupling is bucked onto the pipe and it is end area drifted, the pipe is discharged and rolls down to an outbound conveyor. It is then indexed onto discharge lay racks and can be subsequently subjected to hydrotesting, full-length drift, weight-tally, stenciling, etc.
FIG. 1 shows a typical prior art threading line for threading pipe to produce tubing used in oil and gas wells. Referring then to FIG. 1, there is shown a support or table comprised of spaced rails 10, 12 or other similar members forming a first support side, e.g., the side of rail 10, and a second support side, e.g., the side of rail 12. As seen, the rails 10, 12 are spaced from one another and generally parallel. Rail 12 has a first end 14 and a second end 15 while rail 12 has a first end 17 and a second end 18. Proximate but laterally spaced from first end 14 of rail 10 is a first work station W1 which in the embodiment shown comprises a first lathe 16. A lathe operator P1 is positioned at workstation W1 to operate the lathe 16. Disposed proximate but laterally spaced from the second end 18 of rail 12 is a second workstation W2 which comprises a second lathe 20, a second, lathe operator P2 being positioned at workstation W2 to operate lathe 20.
In the threading operation, the unthreaded pipe sections 22 are held in a rack or feed table comprised of rack members 24 and 26. To commence the operation, a pipe section 22 is indexed in the direction of arrow A along the racks 24, 26 where it drops onto rollers 28 and 30 which form part of a conveyor system well known to those skilled in the art and which can rotate and translate the pipe section 22. As can be seen rollers 28 and 30, are in spaced relationship to one another and are generally aligned with the chucks 32 and 33 on lathe 16. The conveyor comprising rollers 28 and 30 move the pipe section 22 in the direction of arrow B through the chucks 32 and 33 against a stop (not shown) in lathe 16, such that the end 22A of the pipe section 22 is in a position to be contacted by a thread cutting insert 34 carried on a tool post (not shown) on lathe 16 but well understood by those skilled in the art. In the system shown in FIG. 1, the lathe 16 is cutting male or pin threads on the end 22A of pipe section 22. To this end, the pipe section 22 is rotated as the thread cutting insert 34 is moved in the direction of arrow B such that cutting insert 34 cuts an external, helical thread on end 22A of pipe section 22.
Once end 22A has been threaded, the pipe section 22 is released from the chucks 32, 33 and now moved by the conveyor in a direction opposite arrow B onto rails 10 and 12. The pipe section 22, having had end 22A threaded moves in the direction of arrow A to an inspection station where an inspector I1 inspects the threads. Following inspection, the pipe section 22 continues movement in direction A toward the second ends 15, 18 of rails 10, 12, respectively. As shown in FIG. 1, there may be several sections of pipe 22 which have had end 22A threaded. In any event, pipe sections 22 having end 22A threaded are held, in the well known manner, until it is time for the opposite end 22B of a pipe section 22 to be threaded. At such time as threading on end 22B can commence, the pipe section 22 is indexed onto a second conveyor system comprised of driven rollers 36 and 38. As with rollers 28, 30, rollers 36 and 38 are generally in line with chucks 40 and 42 of lathe 20 located at workstation W2. Pipe section 22 is now moved in the direction of arrow C by the conveyor system such that the second end 22B of pipe section 22 moves through the chucks 40, 42 of lathe 20 to a stop position in lathe 20 wherein a thread cutting insert 44 carried by the tool post on lathe 20 can now engage end 22B and, as pipe section 22B rotates, cut male or pin end threads on end 22B of pipe 22 as described above with respect to end 22A. When threading of end 22B is complete, pipe 22 is now moved in the direction opposite arrow C such that the end 22B is no longer in lathe 20. The fully threaded pipe section 22 is then moved onto racks 44 and 46 to an inspection station where inspector 12 can now inspect the threads cut on end 22B. Following inspection, the fully threaded pipe section 22B can be subjected to further operations as described above.
As can be seen from the above description, the conventional, prior art method of machining, e.g., threading, an elongate member, e.g., a pipe, on both ends, is labor intensive in as much as it requires two machine (lathe) operators and two inspectors. In this regard, because of the positioning of worker P1 relative to workstation W1, operating the lathe 16 and inspecting the threaded end of the pipe cannot be done by worker P1 necessitating the need for inspector I1.